The present disclosure relates to a process for treating organic sludge to remove viable pathogenic organisms and reduce vector attraction while significantly reducing residual toxic vapors.
As human population continues to increase, the amount of solid waste generated by human activities also increases. Dealing with this increase in waste has put stress on waste treatment facilities, and new or improved methods of treatment are necessary. Treating solid waste can generate byproducts that are detrimental to the environment, thus, negating the benefits achieved by treatment.
Pollution control authorities such as the Environmental Protection Agency, require that sewage be treated to remove pathogens prior to utilization or disposal of the waste. Sewage is often disposed of in land fills, surface sites, incineration or application to land. Land fill and surface sites are rapidly filling. Incineration requires the use of expensive fuel and contributes to air pollution. A more productive use of waste involves application to land in agricultural production due to the beneficial organic and mineral components of the waste. However, treated waste must be of low toxicity, or non-toxic, to be used in agriculture; as well as being essentially pathogen free. Chemical treatment of organic sludge to destroy microbial pathogens is known in the art. Treatment may be in the form of chemical addition or temperature elevation. Many chemical treatment processes rely on treating sludge a batch at a time or require additional treatment at remote locations due to insufficient on-site equipment.
Chemical treatment of waste often generates toxic byproducts, rendering the treated was inapplicable for use in agriculture. Additionally, toxic vapors may result in areas near treatment facilities experiencing problems with the pollution, including health and unpleasant odors.
Chemical treatment of sewage sludge often produces toxic gases that are difficult to manage and dispose of. While automated processes of chemical treatment of sewage sludge are known in the art, a more efficient and clean process for destroying pathogens and reducing pest attraction is desirable. The use of MITC generating compounds for pathogen reduction and vector-attraction reduction in sewage sludge is known in the art. U.S. Patent Application 2007/0084804 discloses a method for treating sewage sludge with MITC for pathogen reduction. U.S. Patent Application 2014/0290318 discloses a method for treating sewage sludge with MITC for vector-attraction reduction. While both the '804 and '318 applications claim the use of MITC for sewage sludge treatment, neither discloses a method to improve efficiency of MITC use in waste treatment, or discloses a method to use MITC in heavily populated areas without allowing MITC to enter the atmosphere.
Control of toxic gases in sewage treatment systems has been a long-standing problem. Odorous and toxic gases may escape into the environment in proximity to a sewage system which can result in unhealthy and dangerous for those living in the vicinity of such a system. U.S. Pat. No. 4,208,383 relates to the scrubbing of acids and pre-acids such as SO2. The '383 application also relates to the scrubbing of CO2 to generate carbonates and bicarbonates. Scrubbing of toxic gaseous or liquid material from treated waste is not a new concept. However, minimizing additional materials and cost from the process is an ongoing need in the field. Reducing or destroying pathogen content without adding unnecessary toxic material to the process is a goal of research in this area.
Patents in the literature have described numerous methods of dealing with high pathogen containing waste, such as sewage sludge; and the toxic fumes that may result. U.S. Pat. No. 5,422,015 relates to a waste treatment system for removing pathogens from sewage sludge. In the '015 patent, a method of treatment of sludge with an acid, along with a material that will react exothermically with the acid, generate heat to destroy pathogens in the waste. The gases generated by this process may be absorbed by a liquid, rather than exhausted into the atmosphere.
U.S. Pat. No. 4,208,383 relates to a process and apparatus for the absorptive removal of pollutants from waste gases. The '383 patent describes a process whereby gas containing a contaminant is passed from supply tanks into an absorber. The '383 patented process neutralizes the pollutant in the gas through the use of lime, sodium hydroxide or other neutralizing agent.
U.S. Pat. No. 4,793,927 relates to a method for chemically disinfecting sewage with an ammonia source and converting it into an impermeable, friable mass with cement and silicate. A strongly alkaline environment kills bacteria and viruses. While effective, the method of the '927 patent, does not leave the soil in a condition for beneficial agricultural use in many areas.
The expansion of sewage treatment systems into new developments or heavily populated environments can be limited due to real estate unavailability, neighbor aesthetic complaints, zoning restrictions, lack of capital availability or the use of potentially toxic treatment chemicals that may enter the atmosphere or water supply to remove pathogens. These factors can result in the need for sewage to be transported from the source of treatment to a remote location. This process requires additional expense. The alternative, adding air treatment equipment such as conventional scrubbers, as described in the patent literature included above, also requires substantial maintenance effort and expense. However, the present disclosure provides a method and system that improves efficiency when toxic chemicals produce gases that may be detrimental to the surrounding environment, thereby overcoming the above listed problems.